Accession Number : AD0685135

Title :   PHOTOMETRIC MEASUREMENTS OF TURBULENCE IN A HYPERSONIC WAKE,

Descriptive Note : Final letter rept. 1 Oct 66-30 Sep 68,

Corporate Author : MITHRAS CAMBRIDGE MASS

Personal Author(s) : Hill,Jacques A. F. ; Wachsler,Emanuel

Report Date : FEB 1969

Pagination or Media Count : 39

Abstract : Turbulent density fluctuations in the near wake (x/D 10) of a slender body were measured in a wind tunnel at M = 8. Autocorrelations were obtained at several stations as well as cross-correlations for various steamwise separations of the two measurement stations. In addition, power spectra and relative intensities of the fluctuations were measured. To obtain these data, the wake flow was seeded with a small fraction of sulfur dioxide, injected from the base of the model. A two-beam photometer, looking through the wake, was used to measure the fluctuations in the intensity of near-ultraviolet light, which is strongly absorbed by SO2. The signals from the two beams were combined in an analog correlator with a variable delay line. The resulting correlation functions were used to obtain time and space integral scales at various locations in the wake as well as the apparent convection velocity of turbulent eddies along the wake. Examination of these results showed that the observed density fluctuations are associated primarily with corrugations in the turbulent front defining the irregular wake edge. The results in general are consistent with the classic wake analysis for incompressible flows and with ballistic-range measurements of hypersonic wakes far downstream of spheres and cones. (Author)

Descriptors :   (*TURBULENCE, HYPERSONIC CHARACTERISTICS), (*WAKE, SLENDER BODIES), FLOW SEPARATION, CORRELATION TECHNIQUES, POWER SPECTRA, PHOTOMETERS

Subject Categories : Aerodynamics
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE